Hi all. I am learning electronic basics.Q1.Suppose, I have a motor a motor which specifications is. 333mA,6 VDC. And I have only 12 Vdc( car batery)
So what value of resistor should I connect in series?
Q2.Aagian Suppose, I need 50Ω or 18Ω resistor. but I have 100Ωor36Ω. So how what do I do here.?

Well if you just want to connect the motor to see it spin or something then you can use a very sloppy method where you just connect any resistor say....300ohm or something in series and the motor simply won't go over it's maximum revolutions because the resistor will drop the voltage whenever the motor pulls current.
You can use another slightly less sloppy , but crappy method where you use a voltage divider (google it) of say ... 300 and 300 ohm and connect the motor on the output .

A better method you could use is using an LM317 voltage regulator . With an adjustable potentiometer you can controll the voltage from 1.2 volts to whatever voltage you battery gives minus two volts . I suggest trying it , it's probably the easiest and simplest method for connecting a motor and varying its speed . You can google LM317 circuits , you will find tonnes of them .